Cross-sectional and longitudinal analyses of outdoor air pollution exposure and cognitive function in UK Biobank

Abstract

Observational studies have shown consistently increased likelihood of dementia or mild cognitive impairment diagnoses in people with higher air pollution exposure history, but evidence has been less consistent for associations with cognitive test performance. We estimated the association between baseline neighbourhood-level exposure to airborne pollutants (particulate matter and nitrogen oxides) and (1) cognitive test performance at baseline and (2) cognitive score change between baseline and 2.8-year follow-up, in 86,759 middle- to older-aged adults from the UK Biobank general population cohort. Unadjusted regression analyses indicated small but consistent negative associations between air pollutant exposure and baseline cognitive performance. Following adjustment for a range of key confounders, associations were inconsistent in direction and of very small magnitude. The largest of these indicated that 1 interquartile range higher air pollutant exposure was associated on average with 0.35% slower reaction time (95% CI: 0.13, 0.57), a 2.92% higher error rate on a visuospatial memory test (95% CI: 1.24, 4.62), and numeric memory scores that were 0.58 points lower (95% CI: −0.96, −0.19). Follow-up analyses of cognitive change scores did not show evidence of associations. The findings indicate that in this sample, which is five-fold larger than any previous cross-sectional study, the association between air pollution exposure and cognitive performance was weak. Ongoing follow-up of the UK Biobank cohort will allow investigation of longer-term associations into old age, including longitudinal tracking of cognitive performance and incident dementia outcomes.

Association between Exposure to Air Pollution and Total Gray Matter and Total White Matter Volumes in Adults: A Cross-Sectional Study

“…However, the cognitive and neuropsychiatric significance of the amount of volume loss we found associated with exposure to air pollution at the levels used in our study is unknown. In a study also based on data from the UK Biobank, there was only a small association between exposure to air pollution and cognitive function [31], although the association between the amounts of gray-matter and white-matter volume loss that we found and cognitive function, dementia risk, and neuropsychiatric function requires additional research, including in regions where concentrations of air pollutants are higher than in the UK Biobank sample.…”

Air pollution and brain health

“…The authors concluded that a 1µg/m 3 increase in decadal PM2.5 exposure was associated with an increased probability of dementia diagnosis of 1.3% (95%CI 0.4-2.2). The UK investigators using primary care data derived their dementia outcome from the use of Read codes for dementia within the Quality and Three studies reported a measure of cognitive change (based on two measurements) [10,11,14] and one study reported a measure of cognition at one point in time. [15] UK Biobank included several cognitive tests performed on a tablet computer at recruitment: reasoning; reaction time; numeric memory; visuospatial memory; and prospective memory.…”

“…[15] UK Biobank included several cognitive tests performed on a tablet computer at recruitment: reasoning; reaction time; numeric memory; visuospatial memory; and prospective memory. [10] Participants' residential addresses at baseline were used to derive estimated exposure to PM10 and NO2 concentrations derived from EU-wide air pollution maps with 100m×100m spatial resolution based on a LUR model combining data from >1,500 monitoring sites and satellite-derived ground-level concentration estimates. Some data on historical residence locations at 1km×1km resolution were available and used for sensitivity analyses.…”

“…[1] A number of researchers, notably Dr Lilian Calderón-Garcidueñas, have focused on this area for many years, [2] but the volume of literature has recently been rapidly expanding. So far in 2018 there have been four review articles[3-6] published and another nine scientific articles [7][8][9][10][11][12][13][14][15] which were published too recently for inclusion in those review articles.…”

Air pollution and cognition

“…We have better evidence on cognitive development in children than on cognitive decline among older people, for example,7 although the evidence linking incident dementia with long term exposure to air pollution seems increasingly robust, as study findings are replicated 8…”